Edward H. Kalajian

Shear and Deformation Characteristics of Municipal Waste Combustor Bottom Ash for Highway Applications

Municipal waste combustor (MWC) bottom ash from mass-burn (MB) and refuse-derived-fuel (RDF) facilities was evaluated for potential use as highway fill material. MWC bottom ash exhibits acceptable shear and deformation characteristics for many highway applications. RDF ash contains a lower metals percentage than MB ash. The specific gravity of both ashes was found to be a function of metals content. Moisturedensity relationships and unconfined compressive strengths were found to be a function of compaction energy and moisture content. Allowing compacted ash to age increased its unconfined compressive strength. Stress-strain characteristics of both ashes are similar to those of sands. Cohesion exists possibly because of pozzolonic reactions in the bottom ash. The angle of internal friction increased with compacted density. Elastic moduli are a function of density and confining pressure. RDF ash was found to be twice as stiff as MB ash. California bearing ratio results greater than 100 indicated that MB ash could be utilized as road base, and values between 25 and 95 indicated that RDF would be acceptable for use in subgrade and subbase. Bearing ratio results were highly dependent on moisture conditions. Both ashes exhibit little to no swell and should not cause field problems during saturation.

Tensile Behavior of Cast-in-Place and Undercut Anchors in High-Strength Concrete

This paper deals with the pullout capacity, the failure cone geometry, and the load deformation behavior for both cast-in-place and post installed undercut anchors embedded in high-strength concretes with compressive strengths of 7500 and 12000 psi. Cast-in-place anchors where embedded at depths of 4, 6, and 8 in., whereas the undercut anchors were only embedded at a depth of 8 in.. Shallow cone failure angles, ranging from 21 to 28 deg, occurred consistently for all cases regardless of embedment depth, contradicting the 45 deg cone assumed in many design methods. For cast-in-place anchors, current design methods (such as CCD, ACI 349, TVA, TRW-Nelson) over predicted anchor pullout capacity. Over prediction of pullout capacity increased with increasing concrete compressive strength. For the post-installed anchors, the CCD model under predicted anchor pullout capacity, whereas the ACI model over predicted anchor pullout capacity.

The Vertical Holding Capacity of Marine Anchors in Sand and Clay Subjected to Static and Cyclic Loading.

Abstract : The purpose of this investigation was to experimentally measure and then to evaluate the influence, if any, of different loading conditions on the vertical holding capacity of marine anchors embedded in sand and in clay. Small and medium scale indoor laboratory tests and outdoor field tests in a specially constructed tank facility were conducted. The predictions for the holding capacity for anchors in clay and in sand in the shallow mechanism of failure and also for anchors in clay in the deep mechanism, when subjected to static loadings, are found to be in good agreement with cited previous formulas. (Author)

Instrumenting Pencel Pressuremeter Control Unit to Simplify Data Collection, Reduction, and Analysis

The Pencel pressuremeter control unit was instrumented to simplify digital recording, data reduction, and analysis of soil parameters. Digital signals from the instrumentation were collected through a commercially available data acquisition package, known as an automated pressuremeter (APMT), which produced reduced stress-strain data and allowed operators to determine the critical parameters. The instrumented system saved significant time. Data from numerous tests were evaluated for accuracy. Both clays and sands were included in the comparison. A digital pressure transducer was plumbed into the control unit, and a linear potentiometer was connected directly to the piston to produce digital volumes. The digital equipment improved the accuracy of the pressures more than ten-fold and eliminated gear backlash associated with the existing volume counter. The backlash affects the moduli more than the limit pressures, especially those associated with unload-reload loops of stiffer soils. Pressure-versus-time data for each injected volume increment were evaluated to determine when the pressures stabilized. APMT indicated that the pressure stabilized between 10 and 80 s for the sands and clays evaluated. The volume increment stabilization period was defined as the time required for the pressures to stabilize.

Prediction of High Pile Rebound with Fines Content and Uncorrected Blow Counts from Standard Penetration Test

High-displacement piles have rebounded significantly while undergoing an extremely small permanent set per hammer blow in certain soils. This phenomenon, called high pile rebound (HPR), has occurred in many areas of North America. The Florida Department of Transportation identified HPR at six sites in Florida during the process of driving square, precast, prestressed concrete piles into saturated, fine silty-to-clayey sand and sandy-clay soils. Data on pile driving analyzer deflection versus time were used to develop strong correlations between fines content, uncorrected standard penetration test blow counts (NSPT), pile displacements, and rebound. The correlations developed in this study allow the geotechnical engineer to predict whether HPR will occur at a proposed site at which high-displacement piles are planned for driving by a single-acting diesel hammer. A design equation relating pile rebound to NSPT and fines content was developed. The correlations showed that permanent set and rebound were a direct function of NSPT and fines content of the soil at the pile tip. The design equation provides a methodology that allows prediction of HPR during the design phase.

Piezocone Penetration Testing in Florida High Pile Rebound Soils

Abstract Contractors and engineers have experienced pile installation problems while driving high displacement piles with single-acting diesel hammers at Florida Department of Transportation (FDOT) construction sites located throughout the Central and Panhandle regions of Florida. At certain depths during pile driving in saturated soils, rebound exceeding 1 inch (25 mm) was experienced, followed by a small permanent-set during each hammer blow. High pile rebound (HPR) may cause false refusal to occur, stopping the pile driving and resulting in a limited pile capacity. In some cases, rebound leads to pile damage, delaying of the construction project and foundation redesign. In this paper, the response of HPR is investigated using cone penetrometer testing (CPT) and a pile driving analyzer (PDA). PDA data, which yielded the amount and the depth where rebound occurred, produced the pile movement per blow, Nineteen Piezocone soundings were performed at seven FDOT sites in Florida, of which five sites experienced a rebound greater than 0.6 inches (15 mm), one site yielded rebound of 0.35 inches (9 mm), and one site’s rebound was less than the FDOT limit of 0.25 inches (6 mm). In order to improve the knowledge about the soil types producing HPR, a traditional geotechnical investigation on grain-size distribution and soil plasticity allowing for classification using Unified Soil Classification System (USCS) was conducted. Piezocone data were interpreted using the CPT and CPTu soil behavior type (SBT) charts proposed by Schmertmann (1978), Robertson (1990) (i.e., Q-Fr, Q-Rf, and Q-Bq), Eslami and Fellenius (2004), and Schneider et al. (2008). Comparison with classification data from laboratory tests was in excellent agreement with the CPT soil type, indicating that the CPT is a useful tool in evaluation of HPR or “large quake” soils. Correlations between rebound and CPTu data were developed showing that rebound is a direct function of both friction ratio Rf and pore pressure u2.

Strength and Creep Characteristics of Reclaimed Asphalt Pavement-Sand Blend Backfill in Mechanically Stabilized Earth Walls

Using reclaimed asphalt pavement (RAP) as a backfill for mechanically stabilized earth (MSE) walls provides both environmental and economic benefits by allowing in situ recycling for road widening projects. RAP, a well-drained granular material, has lower reinforcing strip pullout strength than A-3 sand and creeps under constant load. The objective of this research was to determine whether blending RAP with A-3 sand would improve RAPs performance in MSE applications. Laboratory specimens of 100% RAP, 100% A-3 sand, and 50% RAP–50% sand blends were compacted by the modified Proctor method and tested for vertical creep with one-dimensional oedometer compression tests at three stress levels to simulate different depths behind an MSE wall. Large-scale test pit testing was performed to determine reinforcing strip ultimate lateral pullout strength; pullout creep at 25%, 50%, and 75% of ultimate pullout; and vertical creep at the three overburden stress levels used in laboratory testing. RAP–sand blends had higher density, friction factors, and pullout strength and developed ultimate pullout strength at lower displacements than either 100% sand or 100% RAP. The RAP–sand blends exhibited more horizontal and vertical creep than 100% sand but significantly less creep than 100% RAP.

Correlations Between PENCEL Pressuremeter, Cone Penetrometer, and Dilatometer Parameters

PENCEL pressuremeter (PPMT), cone penetrometer (CPT), and dilatometer (DMT) tests were performed at three Florida sites. Two were sands and the third was clay. The PENCEL was pushed to the test depth using CPT equipment. During PPMT testing, both a smooth cone tip and a cone tip with a friction reducer were evaluated. Standardized testing procedures were followed for all tests. Initial or lift-off pressures (po), elastic moduli (E), and limit pressures (pL) were determined from the PPMT, whereas po and E values were determined from the DMT. CPT testing produced friction and tip resistances. Manual plus digital pressures and volumes were recorded during pressuremeter testing. Correlations were developed within the engineering parameters obtained from the PENCEL and between the PENCEL, cone, and dilatometer engineering parameters. All correlations matched published values. The PENCEL produced excellent correlations between the initial E and pL as well as the initial E and the reload E. Correlations based on digital elastic and reload moduli, from software called APMT, were higher than those based on the other recorded data. From the comparisons, promising correlations were developed between PPMT initial E values and CPT tip resistances. Promising correlations were also developed between PPMT pL and CPT tip resistances. Consistent ratios existed between PPMT and DMT po values as well as PPMT and DMT initial E values. Smooth and friction reducer cone tips evaluation indicated that soil disturbance, associated with the friction reducer, decreases the engineering parameters, and the friction reducer is not recommended.

Influence of optical fiber coating damage in the light transmissivity characteristics of microbend sensors

A laboratory testing and engineering modeling study was completed to determine the influence of fiber optic coating damage caused by microbend contact on the performance of microbend sensors developed based on relatively low cost single-sided microbending technique using a multimode optical fiber. A testing method was designed, developed and implemented to determine the loads that caused optical fiber glass-coating debonding and coating fracture. Finite Element models of the fiber-deformer system were developed to study the failure modes and predict the stresses that caused this failure. Loads and displacements predicted by Finite Element models were found to be in good agreement with load and displacement values observed during the experimental analyses. It was found that optical fiber coating fracture changes the transmissivity output response but does not affect the recovery of the light transmissivity properties of the optical fiber. Viscoelastic effects were found to influence the behavior of the fiber-deformer system. It was also found that glass-coating debonding and coating fracture during a load-unload cycle are major causes of variability and error during microbend sensor calibration.